Method of introducing molten metal into a continuous casting mold



N. T. MILLS ET AL METHOD OF INTRODUCING MOLTEN METAL INTO June 30, 1970A CONTINUOUS CASTING MOLD Filed Aug. 4, 1969 2 Sheets-Sheet 1 H1 H11)ull "HIH HH 115 II iii Inventors Norman. T. Mills Charles R.JackSon.James Inhi'falleqk fl-H-orneg June 30, 1970 M s ET AL 3,517,726

METHOD OF INTRODUCING MOLTEN METAL INTO A CONTINUOUS CASTING MOLD FiledAug. 4, 1969 2 Sheets-Sheet 3 WIIIVII1II.,-,

WIIIIIIIIIIIIIIA Inventors Norman. T. Mills Char-[es R.J acl son mes m.Hfaller s mmww kasww rHzorriegs United States Patent 3,517,726 METHOD OFINTRODUCING MOLTEN METAL INTO A CONTINUOUS CASTING MOLD Norman ThomasMills, Highland, Charles Richard Jackson, Hammond, and James WoodHalley, Chesterton, Ind., assignors to Inland Steel Company, Chicago,Ill., a corporation of Delaware Continuation-impart of application Ser.No. 779,088,

Nov. 26, 1968. This application Aug. 4, 1969, Ser.

Int. Cl. B22d 11/10 US. Cl. 164-82 14 Claims ABSTRACT OF THE DISCLOSUREA continuous casting process whereby objectionable surface inclusionsare substantially eliminated from the continuous casting and whereinmolten steel is introduced into a continuous casting mold by aninjection means which discharges the molten metal into the mold belowthe surface of the molten metal pool maintained in the mold throughcontrolled streams having an upwardly and outwardly flowing componentwhich contact the solidifying casting surfaces to wash awayobjectionable inclusion materials normally frozen into the casting anddeliver the objectionable inclusion material to the surface of themolten metal pool where they can be readily removed.

Injection nozzles adapted for use with continuous casting molds aredisclosed which comprise tubular sections having circumferentiallyspaced lateral discharge openings for introducing the molten metal intothe mold.

This application is a continuation-in-part application of copending U.S.application Ser. No. 779,088, filed Nov. 26', 1968.

The present invention relates generally to an improved continuouscasting method and apparatus, and more particularly to an improvedmethod of continuously introducing molten metal into an open endedcontinuous casting mold and to submergible injection nozzles used forintroducing molten metal into a continuous casting mold.

In the continuous casting of molten metals and particularly moltensteel, non-metallic inclusion materials, such as aluminum oxide andaluminum silicon oxide and gaseous bubbles of carbon oxides frequentlycause surface defects in the rolled steel because the inclusionmaterials tend to become trapped in or near the surface portion of thecasting adjacent the mold wall. The inclusion materials are particularlyobjectionable, for example, when entrapped in the wider sides of arectangular casting, such as a steel slab, where after rolling intofinished steel, the wider sides form the fiat surfaces of the rolledsteel. Problems of a generally similar nature are encountered in thecontinuous casting of steel billets and blooms.

'Bifurcated submerged injection nozzles have heretofore been used whichdirect the incoming molten metal in streams flowing in diametricallyopposite directions toward the narrower end walls of a mold having anelongated rectangular cross-section, but such nozzles do not preventtrapping the oxide and other objectionable inclusion materials in thewider lateral surfaces of such a continuous casting. As a result, therolled sheets produced from such castings frequently have objectionabledefects along the fiat surface thereof which reduce the value andusefulness of the sheet product.

Molten metal has also been introduced into a continuous casting moldthrough nozzles having a plurality of submerged outlets which aredesigned to impart to the molten metal within the mold a rotating orcircular motion concentric with the longitudinal axis of the inicejection nozzle and mold to obtain more effective mixing of additives(see U.S. Pat. No. 2,224,414 and No. 2,290,- 083) or to prevent coarsegrain crystallization (see US. Pat. No. 3,050,793). Others haveattempted to reduce the surface imperfections in continuous 'bastings byminimizing the contact between the inflowing molten metal and thesolidifying metal skin and by avoiding creating significant currents inthe molten metal in the mold (see French Pat. No. 1,492,871 and U.S.Pat. No. 3,371,- 704). Such efforts, however, have not solved the majorproblem of preventing the trapping of oxides and other objectionableinclusion materials near the surface of the casting, particularly alongthe longer casting surfaces and edges adjacent the corners of acontinuous casting having an elongated rectangular cross-section, andthe products made from such castings contain objectionable surfaceimperfections and are, therefore, less valuable and useful.

It is, therefore, an object of the present invention to provide animproved method and apparatus for continuously casting molten metal in acontinuous casting mold which substantially avoids trapping oxides andother objectionable matter in or near the lateral surfaces of acontinuous casting, particularly in the wider faces of a continuouscasting when the mold has an elongated rectangular form.

It is a further object of the present invention toprovide an improvedsubmergible injection nozzle for introducing molten metal into acontinuous casting mold which reduces the likelihood of entrappinginclusion materials in the lateral surfaces of a continuous casting,such as in the wider lateral surfaces of the casting when the continuouscasting mold has an elongated rectangular shape.

Other objects of the invention will be apparent to those skilled in theart from the following detailed description and claims when read inconjunction with the accompanying drawing wherein:

FIG. 1 is a fragmentary schematic perspective view of the upper sectionof a continuous casting mold which shows a continuous casting beingproduced in accordance with the present invention (the submerged lowerend of the axially disposed injection nozzle being omitted for clarity).

FIG. 1A is a vertical sectional view taken along the line 1A1A of FIG.1;

FIG. 1B is a vertical sectional view taken along the line 1B-1B of FIG.1;

FIG. 2 is a fragmentary schematic side elevational view partially invertical section of an injection nozzle embodying the present inventionand which is operatively disposed in an elongated rectangular continuouscasting mo d;

FIG. 2A is a fragmentary schematic vertical sectional view taken alongthe line 2A2A of FIG. 2;

FIG. 2B is a schematic horizontal sectional view taken along the line2B-2B of FIG. 2;

FIG. 3 is a fragmentary schematic side elevational View partially invertical section of a modified form of injection nozzle operativelydisposed in an elongated rectangular continuous casting mold;

FIG. 3A is a horizontal sectional view taken along the line 3A3A of FIG.3;

FIG. 3B is a horizontal sectional view showing the injection nozzle ofFIGS. 3 and 3A disposed in an alternate operative position with anelongated rectangular continuous casting mold.

FIG. 4 is a fragmentary schematic side elevational view partially invertical section of a further modified form of injection nozzleoperatively disposed in an elongated rectangular continuous castingmold;

FIG. 4A is a horizontal sectional view taken along the line 4A-4A ofFIG. 4;

FIG. 5 is a fragmentary schematic side elevational view partially invertical section of a still further modified form of injection nozzleoperatively disposed in an elongated rectangular continuous castingmold;

FIG. 5A is a horizontal sectional view taken along the line SA-SA ofFIG. 5;

FIG. 6 is a fragmentary schematic side elevational view partially invertical section of another modified form of injection nozzleoperatively disposed in a square continuous casting mold; and

FIG. 6A is a horizontal sectional view taken along the line 6A6A of FIG.6.

It has been found that the foregoing and other objects of the presentinvention can be achieved by introducing molten metal into a continuouscasting mold with a generally vertically disposed mold wall in a mannerwhich establishes a novel dynamic fluid flow pattern of molten metalwithin the pool of molten metal maintained in the upper portion of themold. In the preferred embodiment the novel flow pattern is establishedby forming in the pool a plurality of streams of molten metalhorizontally spaced less than 180 degrees apart which flow toward themold and have at the point of introduction into the mold a fixeddirectional orientation with the axis of each of the streams lyingsubstantially in the same plane and with each of the streams having anupwardly flowing component of sufficient velocity to contact and washthe surface of the solidifying casting supported by the mold wall wherethe metal is initially solidifying at a very high freezing rate andeffectively carry away from the solidifying wall surface of the castingobjectional inclusion materials. The several streams of molten metalflowing upwardly in a generally axial direction carrying theobjectionable inclusion materials preferably substantially merge to forma substantially uniform front so that the molten metal is substantiallyuniformly distributed over the surface of the solidifying casting. Theupwardly flowing streams travel with sufiicient dynamic energy that uponreaching the upper surface of the molten metal, they form a standingwave on the surface of the pool of molten metal adjacent the mold walland then flow inwardly away from the wall toward the axis of the castingforming a central depressed zone or trough.

The invention will initially be described in connection with thecontinuous casting of slabs in an elongated rectangular mold having apair of wider opposed side walls and a pair of narrow opposed end walls.

FIG. 1 of the drawing illustrating a process of continuous casting in agenerally vertically disposed elongated rectangular mold (but which istypical of continuous casting in a mold of any configuration)schematically shows the flow pattern of the molten metal ideallyestablished in a pool of molten metal maintained in the upper endportion of a continuous casting mold 10 and a continuous casting 11 inaccordance with the present invention. The novel flow patternestablished is such that it effects removal from the initiallysolidifying walls of the casting the objectional inclusion materialswhich normally are frozen into the surface of the continuous casting andthereby facilitates forming continuous castings having a substantiallyinclusion-free surface, particularly in the wider lateral surfaces 12,12 of an elongated rectangular casting which corresponds to the exposedflat surfaces of a rolled steel sheet formed therefrom. Theobjectionable inclusion materials which are swept away from the rapidlyfreezing face of the continuous casting preferably collect on thesurface of the central depressed zone or trough 1! formed in the uppermolten metal surface 13 of the casting where they agglomerate to form aslag 14. Because of the low density of the agglomerated slag 14, theslag floats on the surface of the molten metal and is not incorporatedin the casting. The slag that accumulates can be removed by skimming orcan be dis- 4 solved in a fluid artificial slag which can be provided onthe surface of the molten metal.

In accordance with one preferred method of establishing the noveldynamic fluid flow pattern in the pool of molten metal, the infiowingmolten metal is introduced into the continuous casting mold at a pointproximate the longitudinal axis of the mold below the surface of thepool of molten metal in such a manner that a plurality of streams ofmolten metal are formed which are disposed in angularly spacedrelationship in a single horizontal plane and have a fixed directionalorientation at the point of introduction into the mold so that the flowof molten metal is substantially uniformly distributed over theinitially solidifying surfaces of at least the two wider lateral Wallsof the elongated rectangular continuous casting before the streams reachthe upper surface of the pool of molten metal in the mold. It isimportant that the streams of molten metal travel with suflicientdynamic energy so that a substantial proportion of each of the streamsflows outwardly until contacting the surface of the solidifying castingbelow the surface of the pool of molten metal in the mold, then flowsgenerally upwardly in contact with the solidifying casting surfaces, andbefore reaching the upper surface of the molten metal the streams form asubstantially uniform front of flowing metal which at the upper surfaceof the molten metal rolls inwardly away from the walls of the mold. Theforegoing substantially uniform outwardly, upwardly and inwardlycontinuous dynamic flow of molten metal within the pool of molten metalin the mold produces a pronounced standing wave or roll on the surfaceof the molten steel, as indicated at w (see FIGS. 1-1B), which extendsfrom the mold walls inwardly at the upper end of the casting and forms arelatively elongated axial depression or trough t in the upper surfaceof the pool of molten metal between the lateral walls of the castinggenerally in accordance with the idealized flow pattern showndiagrammatically in FIGS. 1, 1A and 1B of the drawing. The objectionableinclusion materials carried upwardly and inwardly by the flowing moltenmetal from the solidifying casting surfaces are concentrated in theupper surface of the trough t.

In carrying out the continuous casting process of the present invention,it has been found that highly satisfactory results are obtained byintroducing molten metal into a continuous casting mold through atubular injection nozzle or snorkel having formed in the lateral Wallsurface adjacent the lower end thereof a plurality of lateral dischargepassages with all having their longitudinal axes lying in substantiallythe same plane and with the spacing between the said passages being lessthan degrees. The discharge passages or outlet means are preferablysymmetrically arranged with respect to a plane passing through thelongitudinal axis of the nozzle; whereby streams of molten metal areinitially directionally oriented in pairs which flow in diametricallyopposite directions. The nozzle si adapted to discharge the molten metalthrough the pas sages below the surface of the pool of molten metal in aplurality of streams which initially have a fixed directionalorientation, and the molten metal is discharged through the passages ata rate which causes the stream to flow with suflicient dynamic energythat a substantial portion of the molten metal in each stream flowsupwardly, preferably uniformly contacting the walls of the solidifyingcasting, and then rolls or flows inwardly to form the desired standingwave along the edge of the mold wall and the axial depression or troughin the upper surface of the pool of molten metal between the mold walls,as previously described.

The injection nozzle which has been found best suited for continuouslytransferring the molten metal from a supply source, such as a tundish,to the interior of an elongated rectangular continuous casting mold inaccordance with the present invention is a cylindrical tubular injectionnozzle closed by a lower end wall and provided with a plurality ofdischarge openings, preferably providing a plurality of pairs ofdiametrically oppositely disposed discharge passages, formed in thelateral surface of the injection nozzle and lying in substantially thesame conical or horizontal plane passing through the cylindrical tubularinjection nozzle.

The size and the cross-sectional form of the tubular injection nozzleand the size, the cross-sectional form and the circumferentialarrangement of the discharge openings in the nozzle can be variedwithout departing from the inventive concept of the present inventionwith the only limitation being that the injection nozzle must establishin the upper portion of the pool of molten metal of the mold a dynamicflow pattern of the type herein described. Thus, for example, thetubular injection nozzle and the discharge openings therein do not haveto be circular and can have an oval, rectangular or other shape, ifdesired. And, although not essential to this invention, the dynamicenergy delivered in an upward direction by the stream flowing upwardlyin contact with the solidifying casting surface can be increased byinclining the longitudinal axis of each of the discharge openingsupwardly from the horizontal where the nozzle in use is disposedvertically with its longitudinal axis parallel to the longitudinal axisof the mold. The metal streams which flow from these upwardly inclineddischarge openings or passages will have a more definite upward angle ofinclination from the horizontal than streams flowing from horizontallydisposed nozzle openings. With a nozzle having discharge openingsinclined upwardly from the horizontal, however, it is important that theupwardly inclined streams of molten metal, preferably originating atabout the axis of the mold, contact the lateral walls of the solidifyingcasting before contacting the upper surface of the molten metal in themold in order to eifect the desired washing action on the wall surfacesof the casting and establish the herein described required dynamic flowpattern within the upper portion of the molten metal pool.

When forming a continuous casting having an elongated rectangularcross-section (i.e. a so-called sla where it is of paramount importanceto avoid surface imperfections in the wide faces of the slab, bestresults are obtained when the discharge passages of the injection nozzleare positioned with respect to the walls of the mold so that none of themolten metal streams flow directly toward the narrow walls of theelongated rectangular mold, as shown in FIGS. 2, 2A, 3, 3A, 4, 4A, 4,5A. The nozzle should also be positioned so that the molten metalstreams wash as much of the wide face as possible by maintaining asuniform a flow condition as possible across each of the wide faces ofthe casting. To maintain substantially uniform molten metal fluid flowconditions across the wide face of an elongated rectangular orslabcasting, it is helpful, but not necessary, to make thecrosssectional area of each molten metal discharge openings proportionalto the axial distance each stream must travel before contacting andwashing the solidifying face of the casting in order to equalize thedistribution of the kinetic energy of the flowing metal over the surfaceof the wider walls of the casting.

The discharge openings in the injection nozzle are preferably circularin form to minimize the frictional resistance to the flow of moltenmetal for an opening of a given cross-sectional area. However, all theopenings do not have to be the same size and discharge openings havingoval or elongated cross-sections can be used, if it is desirable to havethe streams of metal spread or fanned out, as shown in FIGS. 4 and 5 ofthe drawing. Also, if desired, a plurality of single-holed ormulti-holed nozzles can be used in place of a single nozzle to providethe desired herein described dynamic flow and uniform distribution ofthe molten metal within the continuous casting mold.

The injection nozzle 20 shown in FIGS. 2, 2A and 2B of the drawingspecifically illustrates a preferred embodiment of the presentinvention, and the nozzle 20 comprises a suitable refractory cylindricaltubular section 21 having its extreme lower end closed and its upper endconnected with a reservoir of molten metal, such as a tundish (notshown), which has a means for regulating the flow of molten metal to theinjection nozzle 20. The discharge passages or openings 23, 23A and 23Bare formed in the lateral wall of the tubular section 21 at or adjacentthe inner surface of the lower end wall 22 which closes the lower end ofthe nozzle 20 and comprise six cylindrical passages which have theiraxis lying substantially in a conical plane having the apex thereofcoinciding with the longitudinal axis of the nozzle 20. The dischargepassages 23, 23A and 23B are equally spaced about the circumference ofthe nozzle (i.e. spaced 60 apart) with the midpoint of each outletopening spaced axially a short distance from the lower end of the nozzle20. The openings 23A and 23B are of equal size and have about half thecross-sectional area of the remaining openings 23 so that the streams ofmolten metal which travel a greater distance have a larger crosssectional area. Each of the discharge openings 23, 23A and 23B has itsaxis inclined upwardly at an angle of about fifteen degrees from thehorizontal plane when the nozzle 20 is operatively disposed in the mold24. The axis of each of the discharge openings intersects thelongitudinal axis of the nozzle 20 below the midpoint of the dischargeopenings. It will thus be evident that the molten metal flowing fromeach of the openings 23, 23A and 23B will initially form a stream havinga small upward inclination relative to the horizontal but neverthelesstravel generally transversely toward the mold substantially in the sameconical or tranverse plane.

The nozzle 20 is immersed in the pool of molten metal which ismaintained within the open ended continuous casting mold 24 so that thelateral discharge openings 23, 23A and 23B are below the upper surfaceof the molten metal midway between the wide faces 26 and narrow endfaces 27. with the axes of the openings 23A and 23B lying in a verticalplane perpendicular to the vertical planes of the wide mold faces 26, asbest shown in FIG. 2B. The nozzle is disposed so that the smalleropenings 23A and 23B are directed perpendicularly at the midpoints ofthe long side walls 26 of the mold, while the larger openings 23 aredirected obliquely towards the opposite end portions of the wide sidewalls 26, with the result that the wide sides of the casting are washedby the metal emerging from the nozzle and inclusion materials are nottrapped therein.

As a specific example of the invention applied to the continuous castingof steel in a continuous casting mold having a cross sectional dimensionof 37 inches by 8 inches, a fused silica nozzle having the generalconfiguration shown in FIGS. 2, 2A and 2B was used for castinglow-carbon aluminum-killed slabs for rolling to drawingqualitycold-rolled sheet product having a chemical specification of 0.06% Cmaximum, 0.28-0.35% Mn, 0.010% P maximum, 0.030% S maximum and 0.020-0.060% A1. The nozzle had an internal diameter of 2 /2 inches, thedischarge openings 23 hada diameter of 1% inches spaced 60 from openings23A and 23B which had a diameter of inch. The bottom edge of thedischarge openings coincided with the inner bottom of nozzle 20 and theopenings were inclined upwardly forming an angle of 15 with thehorizontal plane. The nozzle Was disposed with the openings oriented asshown in FIG. 2B and located about 6 inches below the surface of themolten metal in the mold. The flow rate of molten steel through thenozzle was between 2 /2 and 3 /3 tons per minute and the linear castingspeed of the slab strand was 60 to inches per minute. A typical 450-tonsample of slabs cast with this procedure and processed into cold-rolledsheet product was subjected to standard methods of surface inspectionpracticed in sheet mills. Over of the sheet product was acceptable forapplication on exposed automobile body parts (hoods, roofs, doors, decklids, fenders) which require superior surface quality.

The flow pattern of the molten metal in the mold 24 and the casting 29which is established by the nozzle 20 under the specified operatingconditions is best shown in FIGS. 2A and 2B, and the standing wave orrolP (w) which surrounds the axial trough (t) is best shown in FIGS. 2and 2A of the drawing. The flow pattern of the molten metal is generallysimilar to the idealized pattern shown in FIGS. 1, 1A and 1B, and theobjectionable inclusion materials commonly present in the mold areeffectively concentrated on the surface of the molten metal in the axialtrough, so that inclusions which normally cause surface steelmakingdefects are substantially eliminated, particularly from the wider faces26 of the elongated rectangular continuous casting.

The modified form of injection nozzle 30 shown in FIGS. 3 and 3A of thedrawing comprises a cylindrical tubular section 31, of a suitablerefractory material, having its lower end closed and its upper endconnected with a tundish (not shown) which is provided with a means forcontrolling the flow of molten metal to the injection nozzle 30. Thelateral discharge passages or openings 33 comprise six equally spaced,equal diameter radially extending cylindrical passages. The axes of theopenings 33 are disposed in a single plane extending transversely of thenozzle 30 and the lower edges of the openings 33 are at or spaced ashort distance above the inner surface of the lower end wall 34 of thenozzle 30. In use, the nozzle 30 is immersed in the pool of molten metalwithin the continuous casting mold 35 so that the lateral dischargeopenings 33 are below the surface of the metal and are directed towardthe mold walls in the manner best shown in FIG. 3A. Thus, the nozzle 30is placed midway between the wide faces 36 and narrow faces 37 of themold 35 with four of the openings 33 symmetrically and obliquelydisposed with respent to the wide faces 36 and two of the openings 33disposed with their axes perpendicular to the wide faces 36.

The streams of molten metal flowing from the discharge openings 33 havea substantial upwardly flowing component, and the flow patternestablished by the nozzle 30 is generally similar to the flow patterndescribed in connection with FIGS. 2, 2A and 2B. The streams of flowingmetal eifect the desired removal of objectionable inclusion materialsfrom the surfaces of the casting, particularly from the wider faces ofthe casting.

In FIG. 3B the nozzle 30B having the same configuration as nozzle 30described in connection with FIGS. 3 and 3A is shown positioned in theupper end of an elongated rectangular continuous casting mold 35B midwaybetween the wide faces 36' and narrow faces 37' with one of thediametrically opposed lateral discharge passages or openings 33aperpendicularly facing the midpoint of each of the narrow faces 37' andhaving the remaining discharge passages 33b directed obliquely towardthe wide faces 36', with the axis of each forming an angle of about 30with the perpendicular through the midpoint of the wide faces 36' sothat the outflowing molten metal is substantially uniformly distributedover the wide faces 36'. While the results obtained with the latterarrangement of the nozzle 30B in the mold 35B are not as good as withthe nozzle arrangement of FIGS. 3 and 3A, there is still a markedimprovement over the results produced by the prior art continuouscasting nozzles.

As a further specific example of the invention applied to the continuouscasting of steel in an elongated rec tangular mold having a crosssectional dimension of 37 inches by 8 inches, a fused silica nozzlehaving the general configuration described in connection with FIGS. 3and 3A was used as shown in FIG. 3B for casting lowcarbonaluminum-killed slabs for rolling to drawingquality cold-rolled sheetproduct having a chemical specification of 0.06% C maximum, 0.280.35%Mn, 0.010% P maximum, 0.030% S maximum and 0.0200.060% Al.

The nozzle had an internal diameter of 2 /2 inches, the horizontallydisposed openings 33a had a diameter of 1 inches spaced 60 from thehorizontally disposed openings 33b which also had a diameter of 1inches. The bottom edge of the openings coincided with the inner bottomof nozzle 30B. With the nozzle 30B positioned in the mold 35B as shownin FIG. 3B, the discharge openings were located about 6 inches below thesurface of the molten metal in the mold. The flow rate of molten steelthrough the nozzle was between 2 /2 and 3 /3 tons per minute and thelinear casting speed of the slab strand was 60 to inches per minute. Atypical 400 ton sample of slabs cast in the foregoing manner andprocessed into cold-rolled sheet product was subjected to standardmethods of surface inspection practiced in sheet mills. About of thesheet product was acceptable for application on exposed automobile bodyparts.

In order to provide a basis for comparing the quality of the rolledsheets obtained from castings produced by the nozzles and process of thepresent invention with castings produced by the prior art submergiblebifurcated nozzles (i.e. nozzles having all the discharge openings inthe lateral wall surface lying in a single vertical plane extendingthrough the longitudinal axis of the nozzle) and straight bore injectionnozzles, low-carbon aluminumkilled steel slabs of the same compositionused with the nozzles of the present invention were cast using varioussubmergible bifurcated and straight bore nozzles. The several bifurcatednozzles which were used had an internal diameter range between 2% and 2/2 inches with dis charge passages between 1 /2 and 2% inches indiameter, and the discharge openings were disposed at angles rangingfrom horizontal to 30 below the horizontal. In all cases the nozzleswere oriented in the mold so that the diametrically opposed openingswere directed toward the narrower end walls of the mold in accordancewith the prior art teaching. The flow rate of the molten steel throughthe nozzle ranged from 2 /2 to 3 /3 tons per minute, and the linearcasting speed of the slab strand ranged from 60* to 80 inches perminute. Using many combinations of casting speed, nozzle dimensions andport angularity, a 700 ton lot of cast slabs was processed intocold-rolled sheet product. None of the nozzle combinations testedproduced a satisfactory proportion of acceptable sheet product. For thetotal sample, only 50% of the sheet product was acceptable forapplication on exposed automobile body parts.

The straight bore nozzles used had an internal diam eter of 1% inches,molten metal flowed through the nozzle at a rate between 1 and 1 /3 tonsper minute, and the linear casting speed ranged from 25 to 40 inches perminute. Over 4000 tons of slabs were cast using the straight borenozzles and only a small portion was suit able for processing to sheetproduct, and of all the sheet product made less than 10% was suitablefor application to exposed automobile body parts.

In processing low-carbon aluminum-killed slabs to hot or cold-rolledsheet product from either conventional cast ingots or continuouscastings, it has heretofore been customary to recondition the slabs byremoving the entire surface or skin of the casting through the use ofmanually operated or mechanized oxy-acetylene torches (i.e. skinscarfing). The objective of skin scarfing is to remove visibleundesirable surface blemishes, such as cracks and scabs, and alsosubsurface inclusions, since both types of inclusions can causeobjectionable surface imperfections in the finished rolled sheetproduct. When using the preferred nozzle shown in FIGS. 2, 2A and 2B andthe modified nozzle in FIGS. 3, 3A and 3B as disclosed herein it wasfound unnecessary to remove the entire surface of the slab (i.e. skinscarfing). Only the occasional visible surface blemishes on the slab hadto be removed (i.e. spot scarfing). The spot scarfing of the test lotsof the present invention which were processed and examined for surfacedefects as previously described involved reconditioning only about ofthe slab surface, whereas skin scarfing requires reconditioning 100% ofthe slab surface. Even with the sharply reduced amount of surfacereconditioned employed on slabs produced in accordance with the presentinvention, over 95% of cold-rolled sheet produced from slabs made usingthe preferred nozzle of FIGS. 2, 2A and 2B was suitable for applicationon exposed automobile body parts and 90% of the sheet product made usingthe modified nozzle as shown in FIG. 3B was suitable for application onthe same class of parts. By making it possible to substitute spotscarfing for skin scarfing, the present invention substantially reducesthe cost of reconditioning slabs preparatory to rolling.

It was found necessary to employ skin scarfing (i.e. 100% surfaceskinning) in processing the slabs which were cast using the severalbifurcated nozzles and straight bore nozzles heretofore described inorder to upgrade the surface quality of the finished sheets producedtherefrom. Even with 100% surface reconditioning through skin scarfing,however, only 50% of the cold rolled sheets made from slabs cast withthe bifurcated nozzles had surface quality suitable for application onexposed automobile parts, and the sheet product made with the straightbore nozzles yielded less than cold rolled sheets suitable for exposedautomobile parts.

The modified form of nozzle in FIGS. 4 and 4A shows that thecross-sectional shape of the nozzle and the discharge ports need not becircular as in FIG. 1 through FIG. 3B but can be any shape as long asthe herein described flow pattern is established in the mold. Thetubular nozzle 40 in FIGS. 4 and 4A has a generally oblong or elipticalcross-section and is provided with four oblong or generally ellipticallyshaped discharge openings 41 spaced symmetrically on opposite sides ofthe minor axis of the elliptical nozzle 40. In use the nozzle 40 ispositioned within the mold 45 with its minor axis pointing toward themidpoints of the wider sides-43 of the mold 45 so that none of thedischarge openings 41 point directly toward the narrow sides 44 of themold 45.

The modified form of nozzle shown in FIGS. 5 and 5A illustrates afurther possible configuration and arrangement of the lateral dischargeports or passages of a submergihle nozzle capable of providing asubstantially uniform flow of molten metal over the wide face of anelongated rectangular continuous casting. The cylindrical tubularimmersion nozzle 50 of FIGS. 5 and 5A is provided with only twodiametrically opposed symmetrical openings 52, 52' which have the shapeof a generally elongated slot the midpoints 53 of which has a lesservertical height than the ends and resembles a bow tie. In use, thenozzle 50 is disposed in the mold 55 with the openings 52, 52' directlyfacing the wider sides 56, 56' of the mold so that the streams flowingfrom the openings 52, 52' will cover substantially the entire widersides 56, 56' of the mold or casting formed therein.

While the foregoing specific embodiments of the invention have relatedto continuous casting in an elongated rectangular mold designed forcasting slabs, the modified form of nozzle shown in FIG. 6 and FIG. 6Aillustrates the application of the present invention to continuouscasting in a generally square mold for casting billets or blooms andwherein the inflowing molten metal is distributed substantiallyuniformly over the surface of the solidifying casting by flowingoutwardly toward the solidifying casting walls with suflicient dynamicenergy to form upwardly flowing streams which wash the solidifyingcasting walls to remove objectionable inclusion materials therefrombefore the inclusion material is frozen into the casting insubstantially the same manner described in connection with continuouscasting in the elongated rectangular molds. The cylidrical tubularinjection nozzle 60 of FIGS. 6 and 6A is preferably provided with fourequally spaced circular discharge openings or passages 62 of equal sizewith the axes thereof lying in a single horizontal plane extendingtransversely through the nozzle 60. In use the nozzle 60 is disposedaxially within the square mold 63 with each of the discharge openings 62disposed below the surface of the molten metal and directly facing themidpoint of a wall 64 of the mold 63 with the axis of each opening beingperpendicular to the mold wall 64.

If desired, the discharge openings or passages 62 in the nozzle 60 forcasting in a square or billet mold can be modified with regards to theshape, number and arrangement as described in connection with thedischarge open ings of the nozzle used with a rectangular mold (seeFIGS. 1-5). Thus, it will be evident that the openings 62 can have anupward inclination relative to a horizontal plane extendingperpendicularly through the longitudinal axis of the nozzle 60,provided, however, the upwards and outwardly flow of the streams ofmolten metal does not intersect the surface of the pool of molten metalmaintained within the upper portion of the casting mold before contactis made with the rapidly solidifying surface of the casting. And, aswhen casting in a rectangular mold, the degree of upward inclinationshould preferably be as large as possible without causing an appreciableamount of the infiowing molten metal to intersect the surface of thepool before contacting the solidifying casting surface.

The present invention is applicable to continuous casting in moldshaving shapes other than the elongated rectangular slab and squarebillet molds specifically illustrated herein, including circular andI-shaped continuous castings, if desired. Other submergible means forintroducing molten metal into the continuous casting mold can also beused, since the present invention is not limited to using the hereindisclosed nozzles and discharge passages. In each of the applications ofthe present invention, regardless of the shape of the mold or theconfiguration and positioning of the means for introducing the moltenmetal into the continuous casting mold below the surface of the pool ofmolten metal in the upper end of the casting, the submerged nozzle orother submergible means for introducing the molten metal shouldsubstantially uniformly distribute the molten metal over at least one ofthe rapidly solidifying surfaces and preferably over all the surfaces ofthe casting which should be free of surface defects with the moltenmetal flowing upwardly along the surface or skin of the solidifyingcasting and wiping the solidifying casting surface from a point belowthe upper surface of the pool of molten metal and the upper edge of thesolidifying casting to the uppermost edge of the solidifying casting,and the upwardly flowing molten metal should have sufiicient dynamicenergy to cause the infiowing molten metal being continually introducedinto the continuous casting mold to wash the solidifying casting surfaceor skin of the casting with an upwardly axially flowing stream to effectremoval of objectionable inclusion materials from the casting surfacebefore the inclusion materials become frozen into the surface of thesolidifying casting or in the immediate subsurface portion of thecasting contiguous with the wall surface in contact with the mold. Thedesired dynamic molten metal flow pattern which effects the desiredwashing of the solidifying casting surface is evidenced within the moldby the formation of a standing wave along the edge of the pool of moltenmetal which on reaching the surface of the pool flows or rolls inwardlyfrom the mold wall preferably forming a trough on the surface of thepool between the mold walls. In the preferred embodiment of the presentinvention the nozzle means employed for introducing the molten metalinto the continuous casting mold have the lateral discharge passagescircumferentially spaced less than degrees with the outlets of all thedischarge passages lying substantially in the same transverse planethrough the nozzle means and with the longitudinal axes of all thepassages having an upward inclination relative to the transverse planethrough the nozzle means forming substantially the same angle with thelongitudinal axis of the nozzle means.

While the specific embodiments illustrating the present invention relateto the casting of steel, the invention can be used in the continuouscasting of any metal or alloy, including copper, aluminum, magnesium andbrass.

We claim:

1. A process for the continuous casting of a molten metal comprising;introducing a stream of a molten metal into an open ended continuouscasting mold having a substantially vertically disposed mold wall at afixed point below the upper surface of a pool of molten metal maintainedin said mold, the said stream being directionally oriented at the pointof introduction into said pool with a major proportion thereofcomprising an outwardly and upwardly flowing component contacting acontinuous casting surface supported by said mold wall before contactingsaid upper surface of said pool, and providing said stream withsufficientdynamic energy to effect after said component has contactedsaid casting surface a continuously upwardly flow of said streamcomprising a substantial proportion of said molten metal in a generallyaxial direction which contacts at least the said area where said castingis initially solidifying and upon reaching said upper surface of saidpool having said stream effecting an inwardly flow away from said moldwall; whereby said solidifying casting surface at least in the areawhere said casting is initially solidifying is contacted with moltenmetal flowing in a generally upwardly axial direction to effect removalof objectionable inclusion material therefrom before said inclusionmaterial is frozen into the solidifying casting surface and then carrysaid inclusion material away from said mold wall and to the central zoneof said upper surface of said pool.

2. A process for the continuous casting of a molten metal comprising:introducing a plurality of streams of a molten metal into an open endedcontinuous casting mold having a substantially vertically disposed moldwall below the upper surface of a pool of molten metal maintained insaid mold with said streams being horizontally spaced and having a fixeddirectional orientation at the point of introduction into said mold andthe axes of all of said streams lying substantially in the same planewhereby a major proportion of each said streams has an outwardly andupwardly flowing component which contacts a solidifying casting surfacesupported by said mold wall before contacting said upper surface of saidpool, and imparting to said streams sufficient dynamic energy to causeeach said component after contacting said casting surface to flowcontinuously upwardly in a generally axial direction in contact withsaid solidifying casting surface at least in the area where said castingis initially solidifying and upon reaching said upper surface of saidpool to flow inwardly away from said mold wall establishing a dynamicflow of molten metal within said pool which forms a standing wave on thesurface of said pool along said mold wall and which extends inwardlyfrom said mold wall; whereby said solidifying casting surface iscontacted with molten metal flowing in a generally upwardly axialdirection which removes from said initially solidifying casting surfaceobjectionable inclusion material before said inclusion material isfrozen into the solidifying casting surface and carries said inclusionmaterial away from said mold wall.

3. A process as in claim 2, wherein said molten metal is substantiallyuniformly distributed over said solidifying casting surface.

4. A process as in claim 2, wherein objectionable inclusion materialcontained in said molten metal which is normally frozen into the surfaceof said casting is carried by said upwardly flowing stream of moltenmetal from said solidifying casting surface and concentrated on thesurface of said pool spaced inwardly from said mold wall and solidifyingcasting surface.

5. A process as in claim 2, wherein said mold is an elongatedrectangular continuous casting mold.

6. A process for the continuous casting of a molten metal comprising;introducing a plurality of pairs of streams of molten metaldirectionally oriented at the point of introduction into an open endedelongated rectangular continuous casting mold having oppositely disposednarrow end walls and wide side walls, said streams being introducedadjacent the longitudinal axis of said mold and below the upper surfaceof a pool of molten metal maintained in said mold, each of said streamsof molten metal being symmetrically disposed with respect to a planethrough the longitudinal axis of said mold and flowing substantiallylinearly outwardly from adjacent said axis in pairs which flow indiametrically opposite directions toward the said side walls of saidmold, and each of said streams being so directionally oriented andprovided with sufficient dynamic energy to produce a continuouslyupwardly flowing component comprising a major proportion of said streamhaving suflicient velocity to contact an initially solidifying castingsurface supported by one of said side walls before contacting said uppersurface and flowing upwardly in a generally axial direction in contactwith said solidifying casting surface and upon reaching said uppersurface of said pool flowing inwardly from said side walls to establisha dynamic flow of molten metal within said upper end of said pool whichforms a standing wave along said side walls and extending inwardly fromsaid side walls and forms a centrally located trough between said sidewalls with objectionable inclusion materials being carried by said flowof molten metal from said solidifying casting surfaces and beingconcentrated on the surface of said trough.

7. A process for continuous casting as in claim 6, wherein one of saidpairs of streams is directionally oriented so that the longitudinal axesthereof are perpendicular to said wide side walls of said mold and atleast two other of said pairs of said streams have their longitudinalaxes obliquely disposed relative to the said wide side walls.

8. A process of continuous casting as in claim 6, wherein one of saidpairs of said streams is directionally oriented so that the longitudinalaxes thereof are perpendicular to said narrow end walls of said moldwith at least two others of said pairs being directionally oriented sothat their longitudinal axes are obliquely disposed relative to the saidwide side walls.

9. A process for continuous casting as in claim 6, wherein each of saidstreams which flow outwardly toward said solidifying continuous castingsurfaces has the cross-sectional area thereof directly proportioned tothe distance each said stream must travel before striking a solidifyingcasting surface in the path of said stream with the streams which travelthe greater distance having the larger cross-sectional area.

10. A process for continuous casting as in claim 6, wherein at least oneof said streams at the point of introduction into said mold has thelongitudinal axis thereof forming an upwardly inclined angle with ahorizontal plane.

11. A process of continuous casting as in claim 6, wherein at least oneof said streams at the point of introduction into said mold has acircular cross-section.

12. A process of continuous casting as in claim 6, wherein at least oneof said streams at the point of introduction into said mold has across-section whose width is greater than the vertical height thereof.

13. A process of continuous casting as in claim 2, wherein at least oneof said streams at the point of introduction into said mold has across-section in the general shape of an elongated horizontal slot withthe midpoint thereof having the narrowest dimension which graduallyincreases in size toward the opposite ends thereof.

14. A process as in claim 2, wherein said mold is a continuous castingmold having four lateral walls of about equal width.

(References on following page) References Cited UNITED STATES PATENTSJunghans. Junghans. Webster. Gunn et a1. Tarmann. Tragner et a1. Astrovet a1.

FOREIGN PATENTS France. France. France.

OTHER REFERENCES Applicants Non-Pat. Citations, Concast News, vol. 7,February 1968, TN1C8, pp. 1, 5 and 6.

10 J. SPENCER OVERHOLSER, Primary Examiner R. S. ANNEAR, AssistantExaminer U.S. cl. X.R. 15 164-134, 135, 281

